Novel Approach to Photocatalytic Removal of Linezolid by Advanced Nano-Biochar/Bismuth Oxychloride Hybrid

Herein, we introduce an innovative nanohybrid material for advanced wastewater treatment, composed of Corchorus olitorius-derived biochar and bismuth oxychloride (Biochar/Bi12O17Cl2), demonstrated in a solar photoreactor. This work focuses on the efficient degradation of linezolid (LIN), a persistent pharmaceutical pollutant, utilizing the unique (photo)catalytic capabilities of the nanohybrid. Compared with its individual components, the biochar/Bi12O17Cl2 hybrid exhibits a remarkable degradation efficiency of 82.6% for LIN, alongside significant chemical oxygen demand (COD) and total organic carbon (TOC) mineralization rates of 81.3 and 75.8%, respectively. These results were achieved within 3 h under solar irradiation, using an optimal composite dose of 125 mg/L at pH 4.3 ± 0.45, with an initial COD and LIN concentrations of 1605 and 160.8 mg/L and TOC of 594.3 mg/L. The nanohybrid’s stability across five cycles of use demonstrates its potential for repeated applications, with degradation efficiencies of 82.6 and 77.9% in the first and fifth cycles, respectively. This indicates the biochar/Bi12O17Cl2 composite’s suitability as a sustainable and cost-effective solution for the remediation of heavily contaminated waters. Further, the degradation pathway proposed the degradation of all of the generated intermediates to a single-ring compound. Contributing to the development of next-generation materials for environmental remediation, this research underscores the critical role of nanotechnology in enhancing water quality and ecosystem sustainability and addressing the global imperative for clean water access and environmental preservation.


INTRODUCTION
The increasing prevalence of antibiotics in aquatic environments, predominantly sourced from inadequately treated domestic and hospital effluents, poses significant ecological and human health risks. 1 Among these contaminants, linezolid (LIN), a newer antibiotic class approved by the FDA, is particularly concerning due to its resistance-inducing capabilities and substantial environmental footprint, with reported concentrations in ecosystems reaching 3−62 μg/L. 2 The emergence of LIN-resistant bacteria underscores the urgent need for advanced wastewater treatment methodologies capable of addressing these biopersistent threats. 3−6 Consequently, the exploration of cost-effective and efficient alternatives has led to the adoption of advanced oxidation processes (AOPs), including photocatalysis, as promising solutions. 7Despite their potential, conventional AOPs like ozonation and electrochemical oxidation are hampered by issues such as sludge production, toxic byproducts, and prohibitive costs. 8,9urther, the electrochemical oxidation process has some shortcomings, such as the high cost of electrodes and the generation of sludge. 10The treatment of heavy metals-bearing sludge can be treated by adding mineralizers during hydrothermal coarsening to recycle heavy metals and reuse the sludge in different industries. 11,12However, treating sludge is complex and expensive.
Photocatalysis has emerged as a sustainable and scalable alternative, offering a pathway to purify water without generating secondary pollutants.However, the practical application of photocatalysis is limited by the inefficiency of traditional photocatalysts under solar irradiation and the quick recombination of charge carriers, 13,14 which occurs in most conventional photocatalysts (TiO 2 and ZnO) and thus suppresses the effective purification of pollutants and broaden the utilization of solar light. 15,16This necessitates the development of novel photocatalytic materials that circumvent these challenges.
In this context, bismuth oxychloride (Bi 12 O 17 Cl 2 ) has gained attention for its stability, nontoxicity, and visible light photoexcitability. 17,18Yet, its applicability is curtailed by the rapid recombination of photogenerated electron−hole pairs. 19o overcome this issue in Bi 12 O 17 Cl 2 , Bi 12 O 17 Cl 2 -based heterojunctions can be constructed using different materials such as BiOBr, 20 β-Bi 2 O 3 , 21 g-C 3 N 4 , 22 rGO, 23 and MoS 2 . 24urthermore, the photocatalyst performance can be improved by controlling the morphology or/and doping the bare catalyst by metals or nonmetals. 25,26However, using the materials mentioned above can increase the treatment cost and the consumption of toxic chemicals, which harm the environment.Thus, the preparation of green and low-cost Bi 12 O 17 Cl 2 -based heterojunctions is imperative for the practical application of the photocatalysis process.
−29 Abdel Azim et al. synthesized biochar from mint stalks for the adsorption of methylene blue, attaining a removal efficiency of 87.5%. 30urther, Elmitwalli et al. prepared a biochar and employed it for the activation of persulfate for the complete degradation of sulfamethazine. 31Herein, Corchorus olitorius stalks collected from the residuals of the food industry were used for the preparation of biochar and composited with Bi 12 O 17 Cl 2 to form a heterojunction photocatalyst for the degradation of LIN for the first time.Li et al. synthesized a composite of AgI/ BiOCl/biochar for the photodegradation of 17α-ethinyl estradiol, achieving a removal efficiency of 98.6% after 12 min compared to 2.5% in the case of BiOCl. 32The employment of biochar can suppress the fast reuniting between charge carriers in bare Bi 12 O 17 Cl 2, as it can act as an electron acceptor. 18,33Additionally, it improves the adsorbability of the composite toward visible light due to the ability of the biochar to narrow the bandgap of the composite. 34,35−38 In this investigation, we unveil for the first time the synthesis and application of a pioneering heterojunction photocatalyst, integrating biochar derived from Corchorus olitorius with Bi 12 O 17 Cl 2 , designed to tackle the persistent challenge of antibiotic contamination in water bodies.This study not only evaluates the composite's exceptional ability to degrade LIN in industrial effluents�an indication of its practical applicabil-ity�but also thoroughly optimizes the operational parameters to enhance its efficiency.By delving into the intricate mechanisms of LIN degradation and elucidating the pathways involved, this research offers unique insights into the photocatalytic process.Crucially, our work transcends traditional photocatalysis paradigms by leveraging the unique electron-accepting properties of biochar and the visible light responsiveness of Bi 12 O 17 Cl 2 , designing a photocatalyst that is both potent and sustainable.The detailed assessment of the composite's performance, including its stability and recyclability across multiple cycles, underscores its viability as a costeffective solution for water treatment.

Synthesis of Biochar Derived from Corchorus olitorius
Waste and Biochar/Bi 12 O 17 Cl 2 Hybrid.The collected Corchorus olitorius stalks were first dried and then ground to a fine powder.Subsequently, washing with water and drying (60 °C) of the powder were performed, and the powder was sieved using a 425 μm mesh sieve and pyrolyzed for 2 h at 600 °C in the absence of oxygen.The obtained biochar was then activated by orthophosphoric acid to increase the surface area and porosity.The activation was performed by adding biochar (50 g) to a beaker containing orthophosphoric acid (H 3 PO 4 , 1000 mL, 0.3 mol/dm 3 ).Subsequently, the mixture was stirred at 100 °C for 30 min and then washed several times with sodium hydroxide and distilled water to neutralize the mixture.The biochar was then dried in an oven at 100 °C followed by pyrolysis in a muffle furnace at 550 °C for 30 min.
To prepare the pure Bi 12 O 17 Cl 2 catalyst, bismuth chloride (1.62 g) was added to absolute ethanol (20 mL).The solution was then mixed for 30 min.Subsequently, 20 mL of NaOH (1.2 M) was added slowly to the mixture, and the mixture was stirred for 3 h.To obtain the bare Bi 12 O 17 Cl 2 powder, the mixture was filtered, and the powder was dried at a temperature of 60 °C for 6.0 h (under vacuum).To fabricate the composite of biochar and Bi 12 O 17 Cl 2 with a biochar mass ratio of 0.31%, Bi 12 O 17 Cl 2 (0.951 g) and biochar (3.0 mg) were mixed in a beaker containing absolute ethanol (20 mL) and stirred for 1.0 h (60 °C).Then, the product was filtered, followed by drying in an oven at 60 °C for 6.0 h (under vacuum).

Experimental Procedures.
The experiments were conducted in a photoreactor, and the details of the photoreactor are provided in Figure S1  optimum catalyst dose, and the optimization of the composite dose was performed using the same range in the case of bare Bi 12 O 17 Cl 2 (pH 4.3 ± 0.45, COD of 1605 mg/L, LIN concentration of 160.8 mg/L, and TOC of 594.4 mg/L).The recyclability of the fabricated hybrid was investigated under five successive cycles, where the catalyst particles were compiled after each run, followed by drying at room temperature for 24 h prior to the next use.

Analytical Methods.
Fourier transform infrared spectroscopy (FTIR) was conducted on a PerkinElmer FTIR Spectrophotometer (FT-IR 1650) to determine the chemical bonds.Scanning electron microscopy (SEM) analysis was performed using a JEOL-SEM instrument integrated with an energy-dispersive X-ray spectrometer to explore the morphology and chemical elements.Transmission electron microscopy (TEM) was also conducted to confirm the morphology.Raman spectroscopy was used to study the chemical structure of the synthesized biochar by using a Confocal Raman microscope (Witec, 300R alpha, made in Germany) at an excited wavelength of 532 nm.The diffraction peaks of the prepared materials were specified by X-ray diffraction (XRD) (Bruker-AXS D8, Germany).X-ray photoelectron spectroscopy (XPS, Thermo Scientific TM K-Alpha) was employed to determine the oxidation states and elemental composition of the synthesized materials.The surface area of the synthesized biochar was estimated using a BET surface area analyzer (BET Belsorp-max automated).Further, the bandgap was estimated using UV−vis diffuse reflectance (Shimadzu).The efficiency of separating electrons and holes was assessed via photoluminescence spectroscopy (PL) by a fluorescence spectrometer (RF-6000; Shimadzu, Japan).
The concentration of LIN was quantified via a UV−vis spectrophotometer (Jasco, V-630 UV−Vis spectrophotometer) by measuring the absorbance at 251 nm, and the ions generated during the photodegradation of LIN were recognized using gas chromatography−mass spectroscopy (GC−MS, Shimadzu) using a gas flow rate of 8 L/min and gas temperature of 200 °C.Total organic carbon was measured using a total organic carbon analyzer (Shimadzu), and chemical oxygen demand was estimated using the standard method described in Standard Methods for the Examination of Water and Wastewater. 39.4.Computational Modeling (Adsorption Energy of Biochar).Computational simulation modeling was carried out for the prepared biochar to assess its adsorption capacity for LIN.The biochar adsorption energy was computationally determined using BIOVIA software.The 3D structure of the biochar on the database does not exist; therefore, graphite was assumed to simulate the biochar structure model as previously reported by Chen et al., Fan et al., and Samy et al. 29,40,41 The oxygen functional groups, i.e., COOH, O−H, and C=O, were simultaneously added to the graphite structure surface to assess the effect of biochar activation on the adsorption process of LIN.LIN 3D structures were downloaded from PubChem and optimized with BIOVIA Forcite for the adsorption capacity of biochar.The binding energy of the adsorption capacity of the biochar with linezolid can be calculated by eq 1. 42 ΔE: is the binding energy, E Biochar@x : is the Biochr@LIN complex energy, E Biochar : is the biochar energy, and E x : is the LIN energy.

RESULTS AND DISCUSSION
3.1.Characteristics of the Prepared Materials.The SEM micrograph shown in Figure 1a shows that the biochar's structure is vessel-like with hollow pores, confirming the efficient adsorption capacity of the synthesized biochar.Further, the surface area of the biochar was nearly 278 m 2 /g, as shown in Figure S2, which reaffirmed the high porosity and adsorption capacity of the biochar.Figure 1b demonstrates the Raman spectra of the synthesized biochar.The bands at 1359.5 and 1581.7 cm −1 are ascribed to the D band and G band of the graphite, which affirmed that the prepared biochar is carbon-rich material. 43Table S1 shows the metal oxides and their weight ratios (TiO 2 , MgO, and Fe 2 O 3 ) that exist in the biochar.
The FTIR spectra in Figure 2a 46 In the case of the composite, no new peaks were noticed for the biochar due to its low content in the composite as well as owing to the excellent distribution of catalyst particles on the biochar surface. 34Additionally, the biochar peaks might interfere with Bi 12 O 17 Cl 2 peaks. 47igure 4a shows the XPS survey spectra reconfirming the chemical constituents of pure Bi 12 O 17 Cl 2 and the composite.The peaks at nearly 158 and 163.5 eV are imputed to Bi 4f 7/2 and Bi 4f 5/2, respectively, in the case of pure Bi 12 O 17 Cl 2 , while the peaks in the case of the composite at approximately 160 and 165.3 eV are indexed to Bi 4f 7/2 and Bi 4f 5/2, respectively, which affirmed the growth of Bi 3+ , as depicted in Figure 4b. 48he presence of Cl was affirmed by the peaks at 198. 5 and  196.44   respectively, in the case of the composite Figure 4d. 49dditionally, the existence of OH and O−Bi−O bonds was affirmed by the peaks at nearly 529 and 530 eV in the case of the bare catalyst and the composite (Figure 4e. 50The peaks at about 287 and 284 eV are because of C 1s in the C−C bond of the biochar, affirming the successful preparation of the composite, as given in Figure 4c. 45Further, the shifts between the peaks in the case of Bi 12 O 17 Cl 2 and biochar/Bi 12 O 17 Cl 2 were due to the introduction of the biochar. The bandgap of the composite was estimated, as shown in Figure S4, and it was nearly 2.6 eV compared to 2.9 eV in the case of Bi 12 O 17 Cl 2 , confirming the role of the biochar in reducing the bandgap.Further, PL spectra in (Figure S5) show that the composite has lower intensity, affirming the improvement of the separation of charge carriers in the case of the composite.photo-oxidation system using biochar loading of 150 mg/L, at pH 4.3 ± 0.45, COD of 1498 mg/L, LIN concentration of 134.6 mg/L, reaction time of 4.5 h, and TOC of 554.8 mg/L as provided in Figure 5a.The removal efficiencies of COD, TOC, and LIN were achieved with high rates in the first 3.5 h, where the removal efficiencies were 42.8, 51.3, and 57.9%, respectively.By prolonging the time was prolonged to 4.5 h, the removal performance was nearly unchanged.The suppression of the removal rate after 3.5 h was due to the loss of biochar particles during the withdrawal of the samples, which reduced the adsorption sites and metal oxides that could adsorb LIN molecules and generate reactive species prior to the illumination by solar light, respectively. 51,52Further, increasing the reaction time could contribute to reducing the binding sites and active sites that are in charge of adsorbing and degrading LIN molecules owing to the accumulation of LIN molecules and their intermediates on the surface. 53Thus, extending the time to 4.5 h just increased the removal ratios by 0.45, 1.81, and 0.5% in the case of COD, TOC, and LIN, respectively.Mensah et al. reported the same conclusion, where the adsorption efficiency did not significantly change with extending the time over 50 min. 54Metal oxides in the biochar are provided in Table S1.The weight ratios of metal oxides (MgO, TiO 2 , and Fe 2 O 3 ) are limited, suggesting that the removal of LIN was mainly through adsorption, not degradation by the generated radicals.

Removal of LIN by the Fabricated Biochar. The removal of LIN was attained using the prepared biochar in a
To find the best biochar concentration, different biochar loadings (50−200 mg/L) were employed under the same reaction time (3.5 h) at pH 4.3 ± 0.45, COD of 1498 mg/L, LIN concentration of 134.6 mg/L, reaction time of 4.5 h, and TOC of 554.8 mg/L, as depicted in Figure 5b).Elevating the biochar loading from 50 to 150 mg/L improved the COD removal percentage from 26.5 to 55.7%, TOC mineralization ratio from 17.8 to 52.2%, and LIN removal efficacy from 18.4 to 62.3% due to the increase in binding sites for adsorption and active sites for generating more radicals. 51However, further augmenting the biochar loading to 200 mg/L did not yield any significant gains in removal efficiencies.This plateau effect is likely due to the biochar particles' aggregation at higher concentrations, which diminishes the effective active surface area, thereby tempering the anticipated advancements in removal capabilities with increased biochar dosages. 55The inhibition of removal efficiency by raising the adsorbent dose was also reported by Ma et   6a.Up to 3 h, the degradation ratio of LIN was 60.8%, while the COD and TOC elimination percentages were 63.4 and 57.8%, respectively.The degradation performance in the case of pristine Bi 12 O 17 Cl 2 was higher than that of bare biochar in a shorter time due to the availability of active sites, which resulted in the production of reactive radicals such as hydroxyl radicals, superoxide radicals, and holes.The inhibition of the degradation rate after 3 h was mainly owing to the decrease of bare catalyst mass with time during sampling as well as because of the coverage of catalyst's particles by LIN molecules leading to the decline of active sites, which reduced the degradation rate. 57To specify the photocatalyst dose that could achieve the best performance, LIN, COD, and TOC removal efficacies were examined under different Bi 12 O 17 Cl 2 doses (50−200 mg/L) at pH 4.3 ± 0.45, COD of 1765 mg/L, LIN concentration of 167.8 mg/L, a reaction time of 3.0 h, and TOC of 653.7 mg/L, as depicted in Figure 6b.The rise of bare Bi 12 O 17 Cl 2 dose to 150 mg/L improved the LIN, COD, and TOC degradation ratios to 60.8, 63.4, and 57.8%, respectively, compared to 39.3, 49.2, and 36.9% in the case of LIN, COD, and TOC, respectively, using 50 mg/L of Bi 12 O 17 Cl 2 .The raising of the catalyst dose ameliorated the removal efficiency owing to the elevation of the generated radicals. 58However, increasing the dose above 150 mg/L did not significantly improve the degradation rate due to the scattering of photons as a result of elevating the catalyst dose. 59Further, the catalyst particles could aggregate in the case of excessive doses, which resulted in lowering the degradation rate. 60Yaghinirad et al. reported that the increase in catalyst dose above 1 g/L resulted in a decrease in the photodegradation percentage of LIN. 61.4.Degradation of LIN, COD, and TOC by the Prepared Composite (Biochar/Bi 12 O 17 Cl 2 ).The degradation efficacies were 82.8, 81.4, and 79.5% in the case of LIN, COD, and TOC, respectively, using 150 mg/L of the composite after 3 h at pH 4.3 ± 0.45, COD of 1605 mg/L, LIN concentration of 160.8 mg/L, and TOC of 594.3 mg/L, as depicted in Figure 7a.The degradation performance in the case of the composite was higher than those of pure Bi 12 O 17 Cl 2 and biochar.The improvement in the case of the fabricated hybrid was due to the potential of the biochar to accept electrons, which ameliorated the separation between charge carriers. 29Additionally, the introduction of biochar could improve the adsorption capacity of the hybrid due to the high surface area of the biochar. 55The increase in irradiation time to 4 h did not enhance the degradation rate due to the explanations mentioned above (catalyst loss during sampling and reduction of active sites with time).
The best composite dose was determined by investigating LIN, COD, and TOC removal efficiencies under different dosages (50−200) mg/L (as given in Figure 7b).According to the results, the optimum dose was 125 mg/L, where the degradation efficacies were 81.3, 75.8, and 82.6% in the case of COD, TOC, and LIN, respectively.However, the degradation rates were 81.9, 78.5, and 83.5% when raising the dose to 200 mg/L.The degradation rate was high when the catalyst dosage increased from 50 to 125 mg/L as a result of the increase of reactive radicals.However, in the case of doses above 125 mg/ L, the scattering effect and aggregation of catalyst particles might be the reasons for the inhibition of the accelerated degradation rate with an excess increase of the dose, as we previously explained.
3.5.Evaluation of the Stability of the Prepared Composite.Different doses (50−200 mg/L) of the prepared hybrid were evaluated over five cycles (Figure 8) for the degradation of LIN with an initial concentration of 160.8 mg/ L, and the time of each cycle was 3 h.The results affirmed the stability of the prepared hybrid under extended reaction time.Under the optimal dose (125 mg/L), the degradation ratios were 82.6, 82.5, 81, 80, and 77.9% in the five cycles, respectively.To reconfirm the stability of the prepared hybrid, XRD was performed after the repetitive cycles, as given in Figure S6, showing the same diffraction peaks in the case of the prepared composite before degradation.The decrease in degradation efficiency in succeeding runs might be due to the loss of catalyst during the withdrawal of samples.Additionally, LIN molecules and their byproducts could be adsorbed on the composite's surface, leading to a decrease in the generated reactive radicals.Therefore, higher doses (150, 175, and 200 mg/L) exhibited higher performance than the 125 mg/L dose in the succeeding runs due to the availability of active sites in spite of the catalyst's loss during sampling and accumulation of pollutant molecules on the active sites because of the high initial catalyst dosage.Table 2 shows a comparison with previous studies to confirm the efficiency of the photocatalyst.According to the comparison, the fabricated hybrid is highly efficient because it could achieve high degradation efficiency in the case of high LIN concentration.   The removal of the pollutants started with the adsorption of pollutants' molecules on the composite's surface, followed by the degradation by the generated radicals.The generated radicals could attack pollutants' molecules and mineralize them to simpler intermediates, as explained in the degradation pathways.To confirm the generation of hydroxyl radicals and superoxide radicals, isopropanol (ISO) and benzoquinone (BQ) were added as free radicals' scavengers with a concentration of 5 mM, where the degradation efficiency greatly decreased to 33.2 and 49.4%, respectively, affirming the prime role of hydroxyl radicals in the degradation system, as given in Figure S7.
The parent pollutant with m/z 338 could be degraded to the intermediates with m/z 312, 336, and 318 due to the opening of the morpholinyl ring, the substitution of fluorine with a  hydroxyl group, and defluorination and dehydrogenation of the morpholinyl ring, respectively. 2Then, the intermediate with m/z 312 could be further degraded to a byproduct with m/z 294 due to defluorination. 67Further, the byproduct with m/z 318 was degraded to intermediates with m/z 350 and 322 owing to the oxidative opening of the dihydro oxazine ring and decarbonylation, respectively. 68All the generated intermediates could be further degraded to a single-ring compound with m/z 159 due to the elimination of the morpholinyl ring as a result of the frequent attack of the reactive species. 69The degradation pathways were suggested based on the identified intermediates, as shown in Figure 9b.3.7.Computational Modeling.The adsorption locator module in BIOVIA was used to quantify the adsorption energy between biochar (adsorbent) and LIN (adsorbate) and study the effect of surface activation of biochar on the binding energy (Figure 10), as reported earlier. 29,70According to the computational modeling results, biochar exhibited an adsorption energy of −14.858 kJ/mol, while surface-activated biochar showed an adsorption energy of −23.192 kJ/mol to capture the LIN.The adsorption energy increased in the case of activated biochar due to the presence of numerous surface oxygen groups such as COOH, OH, and C=O at the activated biochar surface and owing to some hydrogen bonding between H and Cl in linezolid and the surface oxygen group of activated biochar.

CONCLUSIONS
Our investigation has showcased the superior interface and enhanced adsorption capabilities of an activated biochar/ Bi 12 O 17 Cl 2 composite for wastewater treatment.This composite outperformed both its individual components in degrading LIN.The degradation rate of LIN was 82.6%, whereas the COD and TOC mineralization percentages were 81.3 and 75.8%, respectively, in the case of composite's dose of 125 mg/ L (Optimal dose) in 3 h at pH 4.3 ± 0.45, COD of 1605 mg/ L, LIN concentration of 160.8 mg/L, and TOC of 594.3 mg/L.The degradation efficacies of LIN were 82.6, 82.5, 81, 80, and 77.9% in five succeeding runs, which affirmed the stability of the composite over an extended reaction time.The degradation mechanism showed the role of biochar in restraining the reunion between charge carriers.Defluorination and elimination of the morpholinyl ring were the main pathways for the degradation of LIN to simpler byproducts.This study highlights the development of a cost-effective and high-performance system for treating industrial effluents, emphasizing the significant potential of novel material composites in the advancement of (photo)catalytic wastewater treatment technologies.

Data Availability Statement
All data generated or analyzed during this study are included in this published article and its Supporting Information file.

* sı Supporting Information
The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsomega.4c04007.Details of the photoreactors; estimation of valence band and conduction band potentials; experimental setup of the photo-oxidation reactor; adsorption−desorption isotherms of the prepared biochar; TEM image of the fabricated composite; bandgap of the fabricated composite; PL spectra of the fabricated composite; stability of the prepared composite; major reactive oxygen species; and X-ray fluorescence (XRF) for the Corchorus olitorius-derived biochar (PDF) ■

Figure 4 .
Figure 4. (a) XPS survey spectra of bare Bi 12 O 17 Cl 2 and the composite, (b) Bi 4f of bare Bi 12 O 17 Cl 2 and the composite, (c) C 1S of the composite, (d) O 1S of bare Bi 12 O 17 Cl 2 and the composite, and (e) Cl 2p of bare Bi 12 O 17 Cl 2 and the composite.

Figure 5 .
Figure 5. (a) Removal of LIN, COD, and TOC by the prepared biochar.(b) Effect of biochar loading on the removal efficacy of LIN, COD, and TOC.

Figure
Figure (a) Photodegradation of LIN, COD, and TOC over 150 mg/L of pure Bi 12 O 17 Cl 2 in 4 h and (b) effect of Bi 12 O 17 Cl 2 dose on the degradation of LIN, COD, and TOC under a reaction time of 3 h.

Figure 7 .
Figure 7. (a) Photodegradation of LIN, COD, and TOC over the fabricated composite.(b) Effect of composite's dose on the degradation of LIN, COD, and TOC.

Figure 8 .
Figure 8. Reusability of the synthesized composite over five cycles.

3. 6 .
Degradation Mechanism and Degradation Pathways.Figure 9a portrays the degradation mechanism by using the constructed hybrid.The fabricated hybrid could be illuminated by solar light, and then electrons could transfer to the conduction band (CB) after excitation, and holes existed in the valence band (VB) instead of electrons.The electrons in the CB of Bi 12 O 17 Cl 2 could migrate to the biochar's CB, and the holes in the VB of the biochar could move to the VB of Bi 12 O 17 Cl 2 .The charge transfer between the two materials could improve the separation of charge carriers, as affirmed by PL spectra in Figure S5.Then, electrons could react with oxygen to form superoxide radicals and holes could react with hydroxyl ions to produce hydroxyl radicals.The formed superoxide radicals could react with protons to generate H 2 O 2 , and then H 2 O 2 could react with electrons to generate hydroxyl radicals.

Figure 10 .
Figure 10.(a) Geometry-optimized structure of LIN, biochar, and surface-activated biochar.(b) Adsorption of LIN on the surface of the biochar and surface-activated biochar.

Table 1 .
The effect of biochar loading was explored by changing the biochar concentration from 50 to 200 mg/L at pH 4.3 ± 0.45, COD of 1498 mg/L, LIN concentration of 134.6 mg/L, and TOC of 554.8 mg/L.Further, the effects of different dosages of Bi 12 O 17 Cl Characteristics of the Real Industrial Effluents 2 (50−200 mg/L) at pH 4.3 ± 0.45, COD of 1765 mg/L, LIN concentration of 167.8 mg/L, and TOC of 653.7 mg/L on the removal efficacy were explored to specify the show the functional groups on Bi 12 O 17 Cl 2 and biochar/Bi 12 O 17 Cl 2 surfaces.The presence of O−H bond, Bi−Cl, O−Bi−O, Bi=O, and water molecules was confirmed by the bands at 3438.6, 1392.8,846.5, 528.9, and (1622.25 and 1469.9 cm −1 ), respectively in the case of pristine Bi 12 O 17 Cl 2 . 44,45In the case of biochar/Bi 12 O 17 Cl 2 , the bands mentioned above slightly shifted owing to the introduction of biochar.2SEM micrographs of Bi 12 O 17 Cl 2 and biochar/Bi 12 O 17 Cl 2 are shown in Figures 2b,c.SEM micrographs demonstrate the irregular nanosheet structure of Bi 12 O 17 Cl 2 and biochar/

3. Photocatalytic Degradation of LIN, COD, and TOC Using Pure Bi 12 O 17 Cl 2 .
56.563.The degradation of LIN, COD, and TOC was performed using bare Bi 12 O 17 Cl 2 (150 mg/L) at pH 4.3 ± 0.45, COD of 1765 mg/L, LIN concentration of 167.8 mg/L, reaction time of 4.0 h, and TOC of 653.7 mg/L, as provided in Figure

Table 2 .
Comparison with Previous Studies for the Photodegradation of the Linezolid